WIP: PostgreSQL LISTEN/NOTIFY: invalidate wit cache

config.yaml

@@ -16,6 +16,9 @@ postgres.connection.maxidle: -1
 postgres.connection.maxopen: -1
 # Timeout for a transaction in minutes 
 postgres.transaction.timeout: 5m
+# For LISTEN/NOTIFY connections
+postgres.listennotify.minreconnectinterval: 10s
+postgres.listennotify.maxreconnectinterval: 5m
 
 #------------------------
 # HTTP configuration

configuration/configuration.go

@@ -69,6 +69,10 @@ const (
 	varHeaderMaxLength              = "header.maxlength"
 	varEnvironment                  = "environment"
 
+	// Postgres LISTEN/NOTIFY
+	varPostgresListenNotifyMinReconnectionInterval = "postgres.listennotify.minreconnectinterval"
+	varPostgresListenNotifyMaxReconnectionInterval = "postgres.listennotify.maxreconnectinterval"
+
 	// cache control settings for a list of resources
 	varCacheControlWorkItems         = "cachecontrol.workitems"
 	varCacheControlWorkItemEvents    = "cachecontrol.workitemevents"
@@ -180,6 +184,8 @@ func (c *Registry) setConfigDefaults() {
 	c.v.SetDefault(varPostgresConnectionTimeout, 5)
 	c.v.SetDefault(varPostgresConnectionMaxIdle, -1)
 	c.v.SetDefault(varPostgresConnectionMaxOpen, -1)
+	c.v.SetDefault(varPostgresListenNotifyMinReconnectionInterval, time.Duration(10*time.Second))
+	c.v.SetDefault(varPostgresListenNotifyMaxReconnectionInterval, time.Duration(5*time.Minute))
 
 	// Number of seconds to wait before trying to connect again
 	c.v.SetDefault(varPostgresConnectionRetrySleep, time.Duration(time.Second))
@@ -335,6 +341,20 @@ func (c *Registry) GetPostgresConfigString() string {
 	)
 }
 
+// GetPostgresListenNotifyMinReconnectInterval controls the duration to wait
+// before trying to re-establish the database connection after connection loss.
+// After each consecutive failure this interval is doubled, until
+// GetPostgresListenNotifyMaxReconnectInterval is reached.
+func (c *Registry) GetPostgresListenNotifyMinReconnectInterval() time.Duration {
+	return c.v.GetDuration(varPostgresListenNotifyMinReconnectionInterval)
+}
+
+// GetPostgresListenNotifyMaxReconnectInterval see
+// GetPostgresListenNotifyMinReconnectInterval.
+func (c *Registry) GetPostgresListenNotifyMaxReconnectInterval() time.Duration {
+	return c.v.GetDuration(varPostgresListenNotifyMaxReconnectionInterval)
+}
+
 // GetPopulateCommonTypes returns true if the (as set via default, config file, or environment variable)
 // the common work item types such as bug or feature shall be created.
 func (c *Registry) GetPopulateCommonTypes() bool {

gormsupport/listener.go

@@ -0,0 +1,80 @@
+package gormsupport
+
+import (
+	"time"
+
+	"github.com/fabric8-services/fabric8-wit/configuration"
+	"github.com/fabric8-services/fabric8-wit/log"
+	"github.com/lib/pq"
+	errs "github.com/pkg/errors"
+)
+
+const (
+	// ChanSpaceTemplateUpdates is the name for the postgres notification
+	// channel on which subscribers are informed about updates to the space
+	// templates (e.g. when a migration has happened).
+	ChanSpaceTemplateUpdates = "f8_space_template_updates"
+)
+
+// A SubscriberFunc describes the function signature that a subscriber needs to
+// have. The channel parameter is just an arbitrary identifier string the
+// identities a channel. The extra parameter is can contain optional data that
+// was sent along with the notification.
+type SubscriberFunc func(channel, extra string)
+
+// SetupDatabaseListener sets up a Postgres LISTEN/NOTIFY connection and listens
+// on events that we have subscribers for.
+func SetupDatabaseListener(config configuration.Registry, subscribers map[string]SubscriberFunc) error {
+	if len(subscribers) == 0 {
+		return nil
+	}
+
+	dbConnectCallback := func(ev pq.ListenerEventType, err error) {
+		switch ev {
+		case pq.ListenerEventConnected:
+			log.Logger().Infof("database connection for LISTEN/NOTIFY established successfully")
+		case pq.ListenerEventDisconnected:
+			log.Logger().Errorf("lost LISTEN/NOTIFY database connection: %+v", err)
+		case pq.ListenerEventReconnected:
+			log.Logger().Infof("database connection for LISTEN/NOTIFY re-established successfully")
+		case pq.ListenerEventConnectionAttemptFailed:
+			log.Logger().Errorf("failed to connect to database for LISTEN/NOTIFY: %+v", err)
+		}
+	}
+
+	listener := pq.NewListener(config.GetPostgresConfigString(), config.GetPostgresListenNotifyMinReconnectInterval(), config.GetPostgresListenNotifyMaxReconnectInterval(), dbConnectCallback)
+
+	// listen on every subscribed channel
+	for channel := range subscribers {
+		err := listener.Listen(channel)
+		if err != nil {
+			log.Logger().Errorf("unable to open connection to database for LISTEN/NOTIFY %v", err)
+			return errs.Wrapf(err, "failed listen to postgres channel \"%s\"", channel)
+		}
+	}
+
+	// asynchronously handle notifications
+	go func() {
+		for {
+			select {
+			case n := <-listener.Notify:
+				sub, ok := subscribers[n.Channel]
+				if ok {
+					log.Logger().Debugf("received notification from postgres channel \"%s\": %s", n.Channel, n.Extra)
+					sub(n.Channel, n.Extra)
+				}
+			case <-time.After(90 * time.Second):
+				log.Logger().Infof("received no events for 90 seconds, checking connection")
+				go func() {
+					err := listener.Ping()
+					if err != nil {
+						log.Panic(nil, map[string]interface{}{
+							"err": err,
+						}, "failed to ping for LISTEN/NOTIFY database connection")
+					}
+				}()
+			}
+		}
+	}()
+	return nil
+}

gormsupport/listener_test.go

@@ -0,0 +1,62 @@
+package gormsupport_test
+
+import (
+	"sync"
+	"testing"
+
+	"github.com/fabric8-services/fabric8-wit/gormsupport"
+	"github.com/fabric8-services/fabric8-wit/gormtestsupport"
+	"github.com/fabric8-services/fabric8-wit/migration"
+	"github.com/fabric8-services/fabric8-wit/resource"
+	"github.com/stretchr/testify/require"
+	"github.com/stretchr/testify/suite"
+)
+
+type TestListenerSuite struct {
+	gormtestsupport.DBTestSuite
+}
+
+func TestListener(t *testing.T) {
+	resource.Require(t, resource.Database)
+	suite.Run(t, &TestListenerSuite{DBTestSuite: gormtestsupport.NewDBTestSuite()})
+}
+
+func (s *TestListenerSuite) TestSetupDatabaseListener() {
+	s.T().Run("setup listener", func(t *testing.T) {
+		// given
+		channelName := "f8_custom_event_channel"
+		payload := "some additional info about the event"
+		wg := sync.WaitGroup{}
+		wg.Add(2)
+
+		gormsupport.SetupDatabaseListener(*s.Configuration, map[string]gormsupport.SubscriberFunc{
+			// This is the channel we send to from this test
+			channelName: func(channel, extra string) {
+				t.Logf("received notification on channel %s: %s", channel, extra)
+				require.Equal(t, channelName, channel)
+				require.Equal(t, payload, extra)
+				wg.Done()
+			},
+			// This is the channel that we send to from
+			// migration.PopulateCommonTypes() which is called by
+			// gormtestsupport.DBTestSuite internally.
+			gormsupport.ChanSpaceTemplateUpdates: func(channel, extra string) {
+				t.Logf("received notification on channel %s: %s", channel, extra)
+				require.Equal(t, gormsupport.ChanSpaceTemplateUpdates, channel)
+				require.Equal(t, "", extra)
+				wg.Done()
+			},
+		})
+
+		// Send a notification from a completely different connection than the
+		// one we established to listen to channels.
+		s.DB.Debug().Exec("SELECT pg_notify($1, $2)", channelName, payload)
+
+		// This will send a notification on the
+		// gormsupport.ChanSpaceTemplateUpdates channel
+		migration.PopulateCommonTypes(nil, s.DB)
+
+		// wait until notification was received
+		wg.Wait()
+	})
+}

main.go

@@ -9,6 +9,9 @@ import (
 	"runtime"
 	"time"
 
+	"github.com/fabric8-services/fabric8-wit/gormsupport"
+	"github.com/fabric8-services/fabric8-wit/workitem"
+
 	"github.com/fabric8-services/fabric8-wit/closeable"
 
 	"github.com/fabric8-services/fabric8-wit/account"
@@ -140,6 +143,13 @@ func main() {
 		os.Exit(0)
 	}
 
+	// Ensure we delete the work item cache when we receive a notification from postgres
+	gormsupport.SetupDatabaseListener(*config, map[string]gormsupport.SubscriberFunc{
+		gormsupport.ChanSpaceTemplateUpdates: func(channel, extra string) {
+			workitem.ClearGlobalWorkItemTypeCache()
+		},
+	})
+
 	// Make sure the database is populated with the correct types (e.g. bug etc.)
 	if config.GetPopulateCommonTypes() {
 		ctx := migration.NewMigrationContext(context.Background())

migration/migration.go

@@ -12,6 +12,7 @@ import (
 	"text/template"
 
 	"github.com/fabric8-services/fabric8-wit/errors"
+	"github.com/fabric8-services/fabric8-wit/gormsupport"
 	"github.com/fabric8-services/fabric8-wit/log"
 	"github.com/fabric8-services/fabric8-wit/ptr"
 	"github.com/fabric8-services/fabric8-wit/space"
@@ -674,5 +675,16 @@ func PopulateCommonTypes(ctx context.Context, db *gorm.DB) error {
 		log.Debug(ctx, nil, `imported space template #%d "%s"`, idx, t.Template.Name)
 	}
 	workitem.ClearGlobalWorkItemTypeCache() // Clear the WIT cache after updating existing WITs
+
+	// Ensure the WIT cache is cleared in all pods
+	db = db.Exec("SELECT pg_notify($1, '')", gormsupport.ChanSpaceTemplateUpdates)
+	if db.Error != nil {
+		log.Error(ctx, map[string]interface{}{
+			"err":     db.Error,
+			"channel": gormsupport.ChanSpaceTemplateUpdates,
+		}, `failed to notify postgres event subscribers about template updates`)
+		return errs.Wrapf(db.Error, `failed to notify postgres event subscribers about template updates`)
+	}
+
 	return nil
 }